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Growing and Caring for your Yellow Rattle - Rhinanthus Minor

This article aims to help you successfully grow Yellow Rattle.

Background

This is a pretty yellow flower found in traditional hay meadows throughout Northern Europe. It can be difficult to grow, but when the conditions are right it will spread rapidly. Its spread, outside the meadow, is mainly by mechanical means by being caught on machinery, or in a crop such as hay, that has been harvested in July. Some of the seeds are therefore still encapsulated in the plant. Naturally it does not spread far from its parent plant. In the process of hay-making the turning of the hay helps to spread this further. It does not like rough ground when germinating and is therefore confined to the meadows by the hedges and verges where the grasses are not cut or grazed. The plant is a sought-after species for conservationists, who try to encourage colonisation and promote biodiversity. Its preferred habitat is dry fields or meadows. It does not tolerate heavy shade as this delays germination. Its flowering period is between May and July, being at its height in late June.

The seed germinates on the surface of the soil in February or March. At this time of year the seed will have been resting for 6 months and would have stratified due to chilling between 10 and 5 degrees Celsius or spending 6 weeks in a fridge. With the right conditions, and a few warm days, the seed germinates and, depending on your latitude and local weather conditions, it throws up a small, two-leafed shoot that look a bit like jagged-edged stinging nettles. The energy in the seed is soon used up and if the grass is too long it won't be able to take any energy from the sun and will soon perish. This is the main reason why this seed is difficult to grow. If established successfully its roots will parasitize on to a grass, or clover, nearby in April/May. Without Grass the yellow rattle will struggle to thrive and eventually perish. This fine balance between having grass, but not too long, is critical for the survival of Yellow Rattle.

By late May the plant should be beginning to flower. This is orange/red at the base as it opens; turning to yellow in full bloom. The leaves are small, as it is now taking part of its nutrients from the grass and Clovers. Flowering continues for 4 weeks and, by early July, the seed pods have ripened to a golden colour and can be heard rattling in the breeze. If there is sufficient Yellow Rattle the grass would hardly have grown and by the end of June be relatively short and easy to cut. A lot of Yellow Rattle is not good for livestock so it is best to allow the Rattle to set seed thoroughly before cutting for hay. The plant will dry and crumble with little trace left in the hay. Once the Yellow Rattle has died off in Mid-July the grass can grow on freely, rain permitting.

Other common names - Cock's Comb, Hay Rattle, Shackle Bags.

Food plant of the caterpillars of the Grass Rivulet Moth as well as a favourite nectar source of the Bumble Bee.

Get your Yellow Rattle as early as you can from a supplier that you can trust. Last year’s Yellow Rattle won't germinate as well and Yellow Rattle sold in a mixture in the spring also won't germinate in the season of sowing. It is always best to sow this in the Autumn of harvest.

It is important to realise how Yellow Rattle works to understand its place in the field as an annual in a field of perennials. It achieves this by germinating before anything else starts growing. It needs to be able to warm up and have access to moisture and light. If the seed is covered in soil it won't warm up early enough to compete with the grasses. If the grasses are too long at the time of germination it won't be able to get beyond its seedling stage. Finally, if there are too many seeds, only the ones that have found a host plant will thrive.

The seed relies on the sun to warm the seed and not the ground for it to germinate. Its design as a flat seed will keep it naturally on the surface and its large seed coat acts as a solar collector.

Yellow Rattle, and mixtures with it in, must be sown before December of the year of harvest. Broadcast the seed into recently mown (or sowed) grass. Divide the plot and packet into equal areas and quantities. To ensure even distribution sow each sub plot separately, avoiding windy days when the seed can be blown off course. Do not cover the seeds. Scarify and roll and graze the regrowth with sheep or cattle. The animals or machinery will remove the grass and help to tread the seeds into the ground. Ideally grass should be short in January, and every January it may need mowing again. If only a small area is to be sown on a large field, choose a line across the field as the seed will tend to spread in following years.

Growing

Germination begins between February and March in southern England, and later in shady areas or further North. It is so good at germinating that it is partly its downfall. Most of the seeds will germinate, but only a few will survive for one of the following reasons:

Because they cannot find a host grass

The grass is too long

Dry weather

It is advisable to keep stock off these fields from February till August. Allow the Yellow Rattle flowers to ripen and the seeds to blow out. Some of the seeds will be held in a pod, so it is advisable to thrash these out before cutting, especially if you are using a mower with a collector.

Cutting

In any event leave cutting as long as possible. September or October is ideal. Yellow Rattle stops grass growing between May and July. Leaving the cutting later can be more difficult, but the results will be rewarding.

Beware - This is an annual and it will die out in a year if the plants are not allowed to set seed or the grass is too long at the beginning of the year.

Grazing

We have lots of Yellow Rattle in our fields and make and sell lots of hay for horses with no problem. It is all made after the Yellow Rattle has gone to seed and the plants are brittle and mainly crumble and fall out of the hay. Some still remains, especially the stalks, so there seems to be no problem with feeding it dry. We have not seen any evidence that it is poisonous to livestock when green and our sheep graze in the fields from March to April when it is at its most palatable. When it is mature it does not have many leaves, so again it is not very palatable. As with all things if there is nothing else for the livestock too eat, too much Yellow Rattle, of anything, could be a bad thing. However, it has always been in traditional hay meadows and is often made into hay in June without any problems.

Weeding

In Spring go round your wildflower meadows and hoe out any Spear Thistles with a mattock at the rosette stage.
In late June dig up any Docks and Ragwort. Put it straight into a large bag or wheelbarrow to contain any seed that may fall off. Use a fork to dislodge/loosen the root, or turn the sod over and extract the entire root.
Creeping Thistles need to be pulled in Late June. They are easy to pull as long as you don't try to pull any grass at the same time, but you will need a good pair of gloves for this one. Put it straight into a bag. You may need to repeat again as they share a common root system. If persistent and thick, cut in early June. You can also use a selective herbicide, such as Grazeon.
Keep an eye on Himalayan Balsam, as this is starting to become invasive in many places. I suggest keeping this under control before it get out.
Burn all of these species and do not put them on the compost heap.

Bracken - roll or cut this when it is young. If it is a big problem. use a herbicide for bracken such as Asulux.

When using herbicides please make sure you have the appropriate training or use a contractor.

Controlling Yellow Rattle

Some people have asked how to manage Yellow Rattle in their meadows if it gets too dominant. It is relatively easy to reduce Yellow Rattle. Rolling or chain-harrowing the field in April or May will severely reduce it. The later you leave it the more effective rolling is. However you run the risk of damaging other seedlings in the meadows, such as orchids. Graze in May and June. Cut in mid-June or allow the grass to grow over winter so the seeds can't germinate. I would prefer to roll in late April and don't stock the fields after a crop has been cut. That should do the trick and allow maximum grassland perennials to still thrive in the meadows.

Weeding

Keep an eye out for Sow Thistles, Spear Thistles, Ragwort and Docks. Dig up as soon as they appear in the spring.

Environment

Avoid areas shaded by large trees as the seed will struggle to germinate. Where trees cannot be avoided ensure that the fallen leaves are removed as soon as possible. This will have the effect of reducing the fertilisation of the ground by leaf mulch and uncovering the seeds in spring. Dry banks can also be a challenge as they often dry out, taking the Yellow Rattle and finer grasses out as well. Try introducing some Plantain into the bank as a drought tolerant ground cover, as well as some meadow grasses. Wet and boggy ground will support Yellow Rattle as long as it can be cut short in the Summer and grazed in the Autumn. If it is too wet to manage in the Winter then consider choosing some patches which can be easily managed within the area.

Goren Farm has signed up to the Flora Locale terms of code of practice to only sell local provenance seed of the highest quality. Our seed has been deposited in the Kew Millenium Seed Bank as local provenance and Native Origin Yellow Rattle seed.

Please speak to Julian for further details or for bulk purchase – 07770694646.